1. Field of the Invention
The present invention relates generally to mass spectrometry, and more particularly to quadrupole ion guides for mass spectrometers.
2. Description of Related Art
Quadrupole ion guides are well known in the mass spectrometry art for transport of ions between regions of a mass spectrometer instrument. Generally described, such ion guides consist of two pairs of elongated electrodes to which opposite phases of a radio-frequency voltage are applied. The substantially quadrupolar field thus generated radially confines ions within the ion guide such that ions may be transported without substantial losses along an axial path extending between the entrance and exit ends of the ion guide.
In conventional mass spectrometer instruments, ions are transported along a single path extending between an ion source and at least one mass analyzer. Recently, there has been great interest in the development of mass spectrometer systems having more complex architectures, which may require ions to be selectively switched between two or more alternative pathways. For example, a hybrid mass spectrometer may utilize two different types of mass analyzers arranged in parallel, with ions being controllably directed to a selected one of the two mass analyzers. In another example, ions may be switched between a first pathway in which they enter a collision cell and undergo fragmentation into product ions, and a second pathway on which they remain intact. In yet another example, ions generated in one of two different ion sources are selectively admitted to a mass analyzer.
Successful operation of such mass spectrometer instruments require that ion path switching be performed in a manner that does not result in an unacceptable degree of ion loss, and which is non-mass discriminatory. It is also desirable to switch between the plurality of pathways relatively rapidly. The prior art contains few if any devices capable of satisfying these criteria.